1. Field of the Invention
The present invention relates to a developing apparatus preferably used in an image forming apparatus for forming an image on a recording material, such as a copying machine, a printer, a facsimile apparatus and a word processor.
2. Related Background Art
Conventionally, as an arrangement for forming an image through an electrophotographic system, there has been proposed a technique in which a latent image is formed by selectively exposing a drum-shaped electrophotographic photosensitive member (referred to as xe2x80x9cphotosensitive drumxe2x80x9d hereinafter) as an image bearing member uniformly charged by a charging apparatus, and the latent image is developed by a developing apparatus with developer (referred to as xe2x80x9ctonerxe2x80x9d hereinafter) to visualize the latent image as a toner image, and the toner image is transferred onto a recording material, thereby effecting the image recording.
As an example of such a developing apparatus, a developing apparatus as shown in FIG. 10 has been proposed and put to practical use.
In this conventional developing apparatus, a developing container 120 containing nonmagnetic one-component toner is provided with a developing roller 112 as a developer carrying member, a developing blade 116 as a developer regulating member, and a coating roller 119 as a developer coating member.
The coating roller 119 is disposed to be abutted against the developing roller 112 at a position upstream of an abutment position between the developing blade 116 and the developing roller 112 in a rotational direction of the developing roller 112, so that the toner is supplied onto the developing roller 112 by rotating the coating roller in a direction shown by the arrow R2 in FIG. 10.
The toner supplied to the developing roller 112 is sent to the abutment position constituted with the developing blade 116 as the developing roller 112 is rotated.
The toner on the developing roller 112 is brought to a uniform thin layer (toner coat) by the developing blade 116, and, at the same time, charges are applied to the toner layer by friction with the developing blade 116.
Developing bias is applied to the developing roller 112, so that the toner on the developing roller is transferred onto the electrostatic latent image formed on a photosensitive drum 101, thereby visualizing the latent image as a toner image on the photosensitive drum 101.
However, in case of the above-mentioned conventional technique, the following problem arose.
Depending upon environment (temperature, humidity and the like) within which the developing apparatus is installed, a charging amount of charges on the developing roller may become unstable, thereby affecting an influence upon image quality.
In the past, in order to reduce the influence of such environment, a value of the developing bias has been adjusted in accordance with the environment to maintain the image quality constant.
An object of the present invention is to provide a developing apparatus in which a charging amount of charges of developer on a developer carrying member can stably be obtained under various environments.
Another object of the present invention is to provide a developing apparatus having an excellent assembling ability.
The other object of the present invention is to provide a developing apparatus in which position setting of a developer charging member for charging developer on a developer carrying member and that of the developer carrying member can easily be done.